SUMMARY OF WORK A major goal of the laboratory has been to determine the effects of age, gender, lifestyle variables and cardiovascular (CV) disease on cardiac performance, both at rest and during dynamic exercise. We have utilized several techniques to accomplish this mission, including determination of maximal aerobic capacity (VO2max), blood volume measurements and gated cardiac blood pool scanning. Recent examples of these studies are shown. A. To examine the role of intravascular volumes on the augmented aerobic capacity (VO2max) and stroke volume (SV) in endurance trained older athletes compared with untrained subjects, we measured plasma volume and red cell volume VO2max and peak exercise SV in older male runners age 56? 6 yrs and 12 sedentary controls. As anticipated the athletes had higher VO2max (51.5?5 vs. 34?4 ml/kg/min, p<0.01), larger exercise SV index (75?8 vs. 57?13 ml/m2, p<0.05) and higher plasma and red cell volumes than controls. In the combined sample of men , plasma volume was a strong independent prediction of both VO2max (partial r2=0.29, p<0.03) and peak exercise SV index (partial r2=0.30, p<0.03). Thus, the expanded intravascular volumes of endurance trained older men play an important role in their superior exercise cardiovascular performance. B. To examine the effect of age on CV performance during prolonged submaximal exercise (PSE) typical of that performed during everyday life, 40 healthy BLSA volunteers 27 to 84 years old underwent upright cycle ergometry at 70% of peak cycle VO2. Left ventricular (LV) volumes were obtained from gated cardiac blood pool scans every 10 minutes throughout PSE until exhaustion. Although VO2 was maintained constant throughout exercise, arteriovenous oxygen difference declined 11% while cardiac output increased 19% between 10 minutes and end exercise. Of note, the increase in heart rate and LV ejection performance between these points varied inversely with age. Thus, cardiac performance increases progressively throughout PSE but this increase is attenuated in older subjects. C. The contribution of leisure time physical activity (LTPA) patterns to the age-associated decline in treadmill peak aerobic capacity (VO2) was examined in 1116 healthy BLSA subjects 18-95 years old. Although total LPTA was a significant univariate predictor of peak VO2 (r=0.29, p<.001), it accounted for only 1.8% of the variance in peak VO2 per kg weight after consideration of age and body mass index. When LPTA was stratified into low (<4METS), moderate (4-6 METS) and high (<6 METS) intensity categories, the respective correlations with peak VO2 were r=0.07 p=NS, r=0.16, p<.001, and r=0.30, p<.001, indicating that any relationship between LTPA and aerobic fitness is mediated primarily via high intensity activities.